The loss of voluntary control of upper limb muscles is a widespread disability following central or peripheral nervous system lesions. The connection between the intention to perform an action and the coordinated contraction of muscles resulting in limb movements is lost. There is therefore the need to reconnect the intention of the user to the correct sequence of muscular contractions required to perform the movement.
Impaired individuals, such as stroke survivors or spinal cord injured patients, need to undergo long and intense physical rehabilitation sessions in order to recover, at least partially, the lost motor functions. Given the limited availability of resources in modern worldwide healthcare institutions, patients often receive insufficient amount of physical rehabilitation. In addition, a consistent number of patients never recover upper limb functionality even after massive therapy, developing a permanent disability. It is therefore a priority to develop methods and technological solutions aiming at improving the efficiency of the overall rehabilitation processes. To date, the most effective therapy for stroke rehabilitation is the constraint induced movement therapy (CIMT) (Langhorne et al. 2009).
CIMT for stroke rehabilitation is performed restraining the unaffected limb of a patient, for example using triangular bandages or a sling, therefore forcing the patient to an increased use of the affected limb. CIMT has proven its efficacy on patients with sufficient residual mobility (Wolf et al., 2006; Sirtori et al., 2009). However, this therapy cannot be applied on completely paralyzed patients. In fact, residual function is required to complete even the simplest tasks involving the unconstrained limb. Standard criteria for inclusion in CIMT require a patient to display 20 degrees of extension of the wrist and 10 degrees of extension of the fingers. Such relatively high level of motor ability is met by less than 50% of stroke patients (Taub et al., 1998).
Current motor rehabilitation also relies on intensive exercise sessions, robotic rehabilitation systems or peripheral electrical stimulation of nerves and muscles. Intensive exercise sessions are usually limited by the availability of therapist time. Robotic solutions are developed to replace therapists in intensive exercises sessions. However, robotic solutions are still expensive and a limited number of units can be afforded by hospitals, if any. Most importantly, existing robotic solutions (such as InMotion ARM™, Hocoma Armeo™, etc.) only provide passive means of exercising, helping to displace patient's limbs, and are of limited use for completely paralyzed individuals.
Neuroprosthetic devices have the potential of both improving current rehabilitation, by increasing therapy time, and restoring function in permanently disabled individuals. This invention relates to a neuroprosthetic system that allows patient to generate goal-oriented movements of their paralyzed limb. Embodiments of the invention could be used to perform constraint-induced movement therapy on severely paralyzed patients by actuating patient's muscles through neuromuscular electrical stimulation.
Electrical stimulation of upper limbs has shown promising results in promoting voluntary upper limb function recovery (Chae et al., 1998; Alon et al., 2007; Pomeroy et al., 2009). However, in the current medical practice, electrical stimulation therapy is limited by the availability of skilled clinicians in the art and by the lack of a general consensus on how to maximize its efficacy.
Various systems providing electrical stimulation therapy to restore upper limb functions have been proposed. Generally, such systems comprise several invasive or surface electrodes to convey electricity from an electrical stimulator to nerves and muscles of a user. A controller unit generates the electrical current signals Such electrical current is produced according to a predefined sequence of stimulation, or willingly by users.
Several systems to restore upper limb functionality rely on electrodes implanted in the limb to deploy electrical stimulation such as the systems disclosed in Peckham et al., 1992 (U.S. Pat. No. 5,167,229), and in Fang et al., 2002 (US 2002/0188331). Both systems are controlled either by an implanted or external shoulder joystick operated by the user.
Implanting the electrodes solves the problem of maintaining them placed on a specific stimulation site, but requires an expensive and risky surgery. Other systems use surface electrodes, solving the issue by mounting the electrodes on arms-mounted orthosis such as Tong et al., 2007 (US 2007/0179560) or Koeneman et al., 2004, (US 2004/0267331). However, such orthosis are usually very bulky, limiting user mobility, and cannot ensure optimal contact while performing movements, i.e. relative positions and contact area of electrodes and skin changes during use.
Other proposed systems employ cheap surface electrodes, attached to the skin through adhesive conductive glue such as Popovic et al., 2004 (US 2004/0147975). However, the use of surface electrodes requires expert help for positioning said electrodes. Moreover, such standard electrodes are not adapted to guarantee stable positioning over the skin during movements. Most importantly, the glue deteriorates as time goes by favoring detachment of electrodes resulting in discomfort and pain by the users.
Other solutions such as Petrovsky, 1985 (U.S. Pat. No. 4,558,704) addresses only specific functionality of the upper limbs, namely hand opening and closing.
All the above cited systems either allow: 1) simply enabling or disabling the stimulation by use of a switch or button, without providing any means to modulate the stimulation; or 2) modulating the stimulation (and therefore the resulting movement) by providing to the user non-intuitive means to generate a control signal, such as shoulder joysticks. Therefore, they are not suitable to be operated by elderly or cognitive disabled individuals.
A recent system disclosed by Molnar et al., 2009 (US 2009/0099627) describes a system that decodes a movement state directly from the brain of a patient and deliver a therapy accordingly. However, the system requires either implanted electrodes or relies on standard surface electrodes, incurring in the aforementioned problems of maintaining optimal placement.
There is therefore the need to develop a neuroprosthetic device that can be used both as a rehabilitation and assistive technology tool to restore daily life activities involving upper limbs, providing intuitive means to modulate the movements. Moreover, such device should provide easy application of electrodes and ensure electrode placement for long period of time. Finally, to integrate the device into current medical practice it should provide means to improve and extend constraint-induced movement therapy to any type of paralyzed patient.
Scientific referencesSirtori V, Corbetta D, Moja L, Gatti R, “Constraint-induced movementtherapy for uppper extremities in stroke patients”, Cochrane DatabaseSystematic Review, 2009.Wolf S L, Winstein C J, Miller J P, Taub E, Uswatte G, Morris D,Giuliani C, Light K E, Nichols-Larsen D, “Effect of constraint-inducedmovement therapy on upper extremity function 3 to 9 months afterstroke”, JAMA, 2006. Taub E, Crago J E, Uswatte G, “Contraint-induced movement therapy: Anew approach to treatment in physical rehabilitation”, RehabilitationPsychology, 1998.Pomeroy V M, King L M, Pollock A, Baily-Hallam A, Langhorne P, “Electrostimulation for promoting recovery of movement or functionalability after stroke” Cochrane Database Systematic Review, 2009. Alon G, Levitt A F, McCarthy P A, “Functional Electrical StimulationEnhancement of Upper Extremity Functional Recovery During StrokeRehabilitation: A Pilot Study”, Neurorchabilitation and neural repair, 2007.Chae J, Bethoux F, Bohinc T, Dobos L, Davis T, Friedl A, “NeuromuscularStimulation for Upper Extremity Motor and Functional Recovery in Acute Hemiplegia” Stroke 1998. Langhorne P, Coupar F, Pollock A. “Motor recovery after stroke: asystematic review”. The Lancet Neurology, 2009.